My townhouse is all-electric with no garage, no fireplace, and no bbq grill, so no source of carbon monoxide.

What you may save in material you will make up for in engineering and architecture fees. 

Before contracting on the lot, you should check with the local municipality to verify building requirements, current code requirements, list of required documents, surveys, soil tests, engineered plans, etc.Once you have identified your lot and finalized your estimate its time to build.You or your GC will get the permits.For the final build, there are 2 ways to build, as either a cost plus, or fixed price project.Hope this helps, let me know if you have additional questions.

We have installed a permitted tiny house on the land, water meter. electric meter (that can accommodate a large house), and a 5 bedroom septic.

I was talking to the guy that found me the deal and he said it has a Federal Pacific electrical panel and he's saying I'll have to rip out all the sheetrock and redo the wiring in the house as well as the plumbing because it has galvanized pipes.

I have a big garage that has electricity and plumbing already and has a second floor.

Is it worth dividing the electric meter?

You must pay the electric bill.

You need to end goal and then you can reverse engineer the numbers.

There are two types of cost segregation study companies.1 - An engineering firm where a professional will stop by to analyze the property and provide you a report based on his/her findings.2 - An engineering firm that will send you a questionnaire.